Networking
137 bites tagged Networking — interview questions with model answers, and 60-second explainers.
Fetching REST Data with Loading and Error State
Track loading, data, and error; fetch in an effect, check response.ok, parse JSON, handle catch and finally. data fetching with state. ignoring non-2xx responses or leaving loading true on error.
Axios interceptors for auth headers
Interceptors are hooks that run before requests or after responses, centralizing concerns like auth, logging, and token refresh. cross-cutting request handling. attaching the token manually in every call site.
Robust network error handling strategy
Classify errors as 4xx, 5xx, or connectivity; retry transient failures with backoff, surface actionable messages, and check NetInfo. differentiated error handling. one generic catch that retries everything, including 400s.
Axios advantages over fetch
Axios auto-parses JSON, rejects on HTTP error status, and offers interceptors, timeouts, and cancellation out of the box. knowledge of HTTP client ergonomics. claiming fetch rejects on 404 or 500.
The WebSocket Protocol
WebSocket (RFC 6455) is a protocol providing full-duplex, persistent communication over a single TCP connection. It begins as an HTTP request that upgrades, then both client and server can send messages anytime, enabling real-time apps without HTTP's…
Write a frontend-to-backend NetworkPolicy
Set podSelector to app=backend, policyTypes Ingress, one ingress rule with from podSelector app=frontend and ports TCP 8080; the implicit deny handles the rest. Authoring a correct ingress NetworkPolicy.
First NetworkPolicy flips a pod to default-deny
Once any policy selects a pod for a direction, that direction becomes default-deny and only explicitly allowed traffic passes; unselected pods stay open. NetworkPolicy default behavior.
Docker Compose default networking
Compose creates one default user-defined bridge network for the project; all services join it and reach each other by service name via embedded DNS, isolated from other projects. Compose networking internals.
How Compose services reach each other by name
Services share a default network and the web app uses the database's service name as the hostname; Docker's embedded DNS resolves it to the container IP. Compose service discovery.
Technical challenges of a multi-cloud strategy
Data consistency and egress costs across providers, cross-cloud networking and latency, and federating disparate IAM systems, plus operational and tooling overhead. realism about multi-cloud complexity.
Reducing cross-region data transfer costs
Identify cross-region, cross-AZ, and internet egress; co-locate chatty components; add VPC endpoints, CDN caching, and compression. data egress cost awareness. assuming all transfer is free or ignoring NAT gateway egress.
Debug intermittent pod-to-pod connectivity
Scope the failure by path, rule out DNS, inspect kube-proxy iptables and conntrack, check the CNI, then verify cloud security groups and MTU. systematic network debugging. restarting pods with no hypothesis.
Exposing Kubernetes services to the internet
A Service gives stable access and LoadBalancer exposes one service, while Ingress adds L7 host and path routing with TLS for many services. Kubernetes networking layers. conflating the two, or one LB per service.
Security Groups vs NACLs
A security group is stateful and attached to instances or NICs; a NACL is stateless and applied at the subnet. layered network access controls. thinking NACLs are stateful or that security groups support explicit deny rules.
Stable egress IPs for multi-region outbound traffic
Route outbound traffic through NAT gateways with allocated static IPs, or centralize egress so all regions exit through a fixed small IP set you can whitelist. controlling egress IPs at scale.
Site-to-Site VPN vs dedicated interconnect
VPN is quick, cheap, encrypted over public internet with variable latency; Direct Connect or ExpressRoute is a private dedicated link with consistent low latency, high bandwidth, longer lead time and… hybrid connectivity tradeoffs.
Process running but load balancer says unhealthy
The probe path, port, protocol, or expected status may mismatch; a security group may block the probe; the app may be up but not ready. debugging health checks systematically.
Connecting two VPCs privately
VPC peering is simple but non-transitive and full-mesh; a Transit Gateway scales hub-and-spoke; PrivateLink exposes one service narrowly. VPC connectivity options and their scaling tradeoffs.
How cloud DNS resolves a URL to an IP
Recursive resolver queries root, then TLD, then your authoritative cloud DNS zone; the matching record returns an IP, cached per TTL. end-to-end DNS resolution flow. skipping the recursive resolver or caching.
Layer 4 vs Layer 7 load balancers
L4 routes on IP and TCP/UDP ports fast and protocol-blind; L7 inspects HTTP for host, path, and headers. OSI model and load balancer routing knowledge. claiming L7 is always better.
Public and private subnet VPC design
Web server in a public subnet routed to an internet gateway, database in a private subnet with no inbound from the internet, NAT for outbound. core VPC networking. placing the database in a public subnet or relying only on.
Optimizing low-latency VM-to-VM networking
Cluster placement groups, enhanced networking and SR-IOV, larger instances for more bandwidth. networking performance depth. ignoring that tight placement concentrates instances in one AZ, trading availability for latency.
Hybrid cloud bursting from a VMware footprint
Evaluate VMware Cloud on AWS, Azure Arc, Outposts; address connectivity, identity, and data gravity. hybrid architecture and networking depth.
Add a default header to every URLSession request
Set httpAdditionalHeaders on a URLSessionConfiguration, build the session from it, mention per-request overrides win. Knowing URLSession is configured, not just used. Subclassing URLRequest or mutating every request by hand.
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